monochromat
monochromate

Therefore, a monochromat would be able to distinguish about 100 colors.

A rod monochromat is truly unable to see any color and can see only shades of grey.

A cone monochromat can have good pattern vision at normal daylight levels, but will not be able to distinguish hues.

This means that a monochromat can see 100 different colors, a dichromat can see 10,000 different colors, a trichromat can see 1,000,000 different colors, a tetrachromat can see 100,000,000 different colors, and a pentachromat can see 10,000,000,000 different colors.